The invention relates to a control lever assembly, and more particularly, to a control lever assembly for a powershift transmission shift control which operates in a "pulse" or "bump shift" manner.
Electronically controlled powershift transmissions require an operator control device, such as one or two shift levers, which generate control signals which are utilized to control the transmission. For example, U.S. Pat. No. 4,425,620, issued 10 Jan. 1984 to Batcheller et al., and U.S. Pat. No. 4,855,913, issued 8 Aug. 1989 to Brekkestran et al., both show transmissions controlled in response to two levers: a mode lever and a pulser or upshift/downshift lever. Also, a powershift transmission with two control levers is provided on a 700 Series Motor Grader manufactured by Champion Road Machinery.
Various designs have been proposed whereby a single lever performs both the mode selecting and the upshift/downshift functions. For example, a single lever shift control is available on the 8030 Series Tractor manufactured by Ford-New Holland. In this single lever design, the lever is movable fore-and-aft to forward, neutral and reverse positions, and the lever is movable laterally from each of the forward, neutral and reverse positions to upshift and downshift sub-positions. However, this design provides no park position and the park function is accomplished with a separate device. Also, this design requires that a locking ring mounted on the lever be lifted to move the lever forward and backward from its neutral position.
Also, U.S. Pat. No. 4,442,730 issued 17 April 1984 to Snoy, shows a transmission controlled in response to a single lever movable between forward, neutral and reverse positions and movable laterally from the forward and reverse positions to upshift and downshift positions. U.S. Pat. No. 4,991,454 issued 12 Feb. 1991 to Bulgrien, shows a pattern for a transmission shift control lever wherein the pattern includes forward, neutral and reverse positions and the lever is movable from each of the forward, neutral and reverse positions to upshift and downshift sub-positions. U.S. Pat. No. 4,926,172 issued 15 May 1990 to Gorsek and U.S. Pat. No. 5,243,871 issued 14 Sep. 1993 to Weiten, both show lever mechanisms with a guide which defines a shift pattern similar to the pattern described in the Bulgrien patent. In these single lever designs, the upshift/downshift function requires movement of the lever in directions which are transverse to the direction of movement which performs the mode selecting function.
A different single lever shift control is available on the 6100 Series Tractor manufactured by Agco White. In this single lever design, there is a single linear fore-and-aft extending forward-neutral-reverse slot with forward upshift, noshift and downshift positions at a forward end of the slot and reverse upshift, noshift and downshift positions at an aft end of the slot. However, this design provides no park position and the park function is accomplished with a separate lever. Also, this design requires that a separate push button mounted on the top of the lever be depressed to move the lever out of its neutral position. Such a lever shift control is complicated to operate and there is no "race track" lever path which clearly indicates the shift functions being performed.
It would be desirable to have a single lever type shift control lever which performs both the forward-neutral-reverse mode selecting function and the upshift/downshift function in response to natural or intuitive lever motions, which includes a park position and which does not require a push button or a locking ring.